<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>07-变量的使用-更新</title>
</head>

<body>
  <script>
    //1. 声明一个年龄变量
     let  age = 18
    // //2. 赋值  = 是赋值
      age = 20
    // //3. 输出age变量
    console.log(age)
  </script>
</body>
</html>